I know you've heard me talk about these before, but they are one of my absolute favorite crafting items. I love to mark the edges of my papers with these, use them with stamps - whatever! They come in so many colors! I recently won a Michael's gift card from Traci and since they didn't really have any Prima's that I wanted, I ended up buying more Cat's Eye Chalks.
Of course, there are colors that I use more than the others - but you can never have enough if you ask me!